The invention relates to vessels for cryogenic liquids, which comprise an inner container and an outer container which are positioned with respect to each other and are thermally decoupled from each other by a vacuum insulation layer. Cryogenic liquids are to be understood as meaning liquefied gases, for example helium, nitrogen or oxygen, but in particular hydrogen. Their temperature in the liquid state is only a few degrees Kelvin. Vessels of this type are used in space travel and will also be used in the future in motor vehicle manufacturing. In these applications, a low weight and best possible heat insulation are important.
When used in motor vehicles using hydrogen as fuel, these requirements are extremely applicable because weight increases the masses to be moved and therefore the consumption of fuel. Added to these, however, are also the typical requirements of everyday use, for example those for increased safety and those for particularly good heat insulation. Since it may be possible for a vehicle in every-day use not to be operated for weeks on end, the evaporation losses have to be minimized.
In principle, there are two possibilities for storing liquid hydrogen: in a pressure vessel—in which case the pressure rises due to evaporation; or under atmospheric pressure—in which case the evaporated gas escapes. Evaporation losses have therefore to be minimized in both cases.
Known generic vessels for liquid hydrogen are composed of metal, generally of a light metal. Nevertheless, and despite storage approximately at atmospheric pressure, for reasons concerned with the required, precise assignment of inner and outer containers, and, in the case of the vacuum prevailing in between, for reasons concerned with strength and safety, wall thicknesses are required which continue to make vessels of this type extremely heavy.
Although a container composed of fiber-reinforced material is known from space travel (U.S. Pat. No. 3,392,865), and although its wall is built up from a series of different layers (including an insulation layer and a gas-collecting layer), it does not involve two containers constructed one inside the other.
It is therefore the object of the invention to design a vessel of the generic type in such a manner that, with the lowest possible weight and lowest possible costs in series production, it offers the best possible heat insulation and also satisfies all other safety requirements.